1. Field of the Invention
The present invention relates to a pen nib comprising a rod-like core made of a thermoplastic synthetic resin and having axially continuous ink-conducting capillary channels of suitable cross-sectional shape, which may suitably be employed in writing instruments for fine lettering or for drawing fine lines.
2. Description of the Prior Art
Up to the present, the large majority of writing instruments for fine lettering or tracing fine lines, which are generally available on marketplace, have employed polyacetal resin pen nibs of relatively small diameter.
However, due to the practical limitations arising from insufficient flexural strenght of conventional polyacetal resin pen nibs, the length of exposure of the writing tip from the pen nib holder in these writing instruments has been restricted. When the polyacetol resin pen nib has an outer diameter of 0.8 mm, for example, these instruments are normally provided with a writing tip exposure length of from 1.0 to 1.5 mm in order to avoid breakdown or snap of the pen nibs when applied with the writing pressure, at the sacrifice of flexible and/or resilient writing feel which is an important requirement to be fulfilled. Thus, there has been demand for the development of synthetic resin pen nibs with an excellent flexural strength, that do not break or snap even at larger exposure lengths.
The above-described type of polyacetal pen nib develops from about 0.015 to 0.250 mm of tip wear per 100 meters of writing on commercially available high-grade paper or high-grade photocopier paper under a writing pressure of about 100 g. As a result, under the abovementioned restricted writing tip exposure length and depending on the type of paper used, the writing tip may excessively wear down to have a writing life of only about 500 meters. This has prompted calls for the development of a synthetic resin pen nib with good wear resistance.
In addition, considerable variation may arise in the writing life of the writing instrument, depending on whether the principle solvent in the ink composition used is water, an organic solvent, or a mixture of the two. A synthetic resin pen nib that combines good chemical resistance and resistance to organic solvents with the physical properties already noted above has thus been awaited.